Forging is a metal forming process used to shape and strengthen many types of components. For example, forging is used to manufacture engine connecting rods, cam shafts, gear blanks, bushings, hammers, wrenches, golf clubs and other well known objects. Forging is advantageous over other metal forming processes since it provides components with increased strength relative to the original material. Strengthening occurs due to change in the grain structure of the material during component shaping. Forging can be performed at various temperatures. Cold forging is typically performed with a work piece at room temperature. This process is used for relatively small components or when a small amount of material flow is required. Hot forging is typically performed with the work piece at an elevated temperature but below the material's melting point. This process is used for relatively large components or when a large amount of material flow is required.
Forging presses are typically driven by mechanical components, such as eccentric shafts, cranks, and screws, or hydraulic actuators. A forged component takes the shape of a die tool set cavity on the forging press. When annular components are forged, the die tool set typically includes a die, upper and lower punches, and core rods. The die surrounds the work piece in a radially outward direction. The upper and lower punches compress the work piece in an axial direction. The core rods hold and complete internal voids in the work piece.
Forging is typically used for steel or steel alloy components. However, processes for forging other materials, such as aluminum, copper, and titanium, are also known in the art. Forging processes can also be used to shape sintered powder metal blanks. After a sintering process, a powder metal blank has the approximate shape of the final component. However, a forging process is typically required for the component to meet manufacturing tolerances.
In hot forging operations, core rods are used to create and shape internal void shapes. The core rods are subjected to extreme heat and pressures and tend to wear significantly as the number of press cycles increases. Eventually, the core rods need to be replaced to make parts that are within specifications. In addition, sharp corners are often required for components which include internal splines. Wear of the core rod occurs even more rapidly on these sharp corners. Considering the limitations of the previous forging core rods, a need exists for a core rod that is resistant to wear compounded by heat and pressure, yet is capable of producing components with high precision.